A novel poly(N-vinylcaprolactam)-based well-defined amphiphilic graft copolymer synthesized by successive RAFT and ATRP

A series of well-defined amphiphilic graft copolymers consisting of a hydrophobic poly(tert-butyl acrylate) (PtBA) backbone and hydrophilic poly(N-vinylcaprolactam) (PNVCL) side chains were synthesized via the combination of reversible addition-fragmentation chain transfer (RAFT) polymerization, atom transfer radical polymerization (ATRP), and the grafting-from strategy without any polymeric functional transformation. RAFT homopolymerization of tert-butyl 2-((2-bromopropanoyloxy)methyl) acrylate (tBBPMA) was first performed to give a well-defined Br-containing PtBBPMA backbone with a low polydispersity (M-w/M-n - 1.22). PNVCL side chains were grown from the backbone via straightforward ATRP of N-vinylcaprolactam using CuBr/Me(6)Cyclam as the catalytic system in 1,4-dioxane to afford the target PtBA-g-PNVCL amphiphilic graft copolymers with narrow molecular weight distributions (M-w/M-n <= 1.32). The self-assembly behavior of these graft copolymers in aqueous media was studied by fluorescence spectroscopy and transmission electron microscopy (TEM), and furthermore, their thermo-responsive behavior was investigated by UV-vis and dynamic light scattering (DLS). Finally, the hydrophobic PtBA backbone was selectively hydrolyzed into a hydrophilic PAA backbone without affecting PNVCL side chains in the acidic environment to provide PAA-g-PNVCL graft copolymers.